From 31f3ee328b2a471999acca527e3a83d6af3c75d9 Mon Sep 17 00:00:00 2001
From: Martin Sperl <kernel@martin.sperl.org>
Date: Fri, 22 Apr 2016 17:17:37 +0000
Subject: [PATCH] Revert "dmaengine: bcm2835: Add slave dma support"

This reverts commit 8a349301238aabb40c9da5ca8c8492b6b8d146f6.
---
 drivers/dma/bcm2835-dma.c | 206 ++++------------------------------------------
 1 file changed, 14 insertions(+), 192 deletions(-)

--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -1,10 +1,11 @@
 /*
  * BCM2835 DMA engine support
  *
+ * This driver only supports cyclic DMA transfers
+ * as needed for the I2S module.
+ *
  * Author:      Florian Meier <florian.meier@koalo.de>
  *              Copyright 2013
- *              Gellert Weisz <gellert@raspberrypi.org>
- *              Copyright 2013-2014
  *
  * Based on
  *	OMAP DMAengine support by Russell King
@@ -94,8 +95,6 @@ struct bcm2835_desc {
 	size_t size;
 };
 
-#define BCM2835_DMA_WAIT_CYCLES	0  /* Slow down DMA transfers: 0-31 */
-
 #define BCM2835_DMA_CS		0x00
 #define BCM2835_DMA_ADDR	0x04
 #define BCM2835_DMA_SOURCE_AD	0x0c
@@ -112,16 +111,12 @@ struct bcm2835_desc {
 #define BCM2835_DMA_RESET	BIT(31) /* WO, self clearing */
 
 #define BCM2835_DMA_INT_EN	BIT(0)
-#define BCM2835_DMA_WAIT_RESP	BIT(3)
 #define BCM2835_DMA_D_INC	BIT(4)
-#define BCM2835_DMA_D_WIDTH	BIT(5)
 #define BCM2835_DMA_D_DREQ	BIT(6)
 #define BCM2835_DMA_S_INC	BIT(8)
-#define BCM2835_DMA_S_WIDTH	BIT(9)
 #define BCM2835_DMA_S_DREQ	BIT(10)
 
 #define BCM2835_DMA_PER_MAP(x)	((x) << 16)
-#define BCM2835_DMA_WAITS(x)	(((x) & 0x1f) << 21)
 
 #define BCM2835_DMA_DATA_TYPE_S8	1
 #define BCM2835_DMA_DATA_TYPE_S16	2
@@ -135,14 +130,6 @@ struct bcm2835_desc {
 #define BCM2835_DMA_CHAN(n)	((n) << 8) /* Base address */
 #define BCM2835_DMA_CHANIO(base, n) ((base) + BCM2835_DMA_CHAN(n))
 
-#define MAX_NORMAL_TRANSFER	SZ_1G
-/*
- * Max length on a Lite channel is 65535 bytes.
- * DMA handles byte-enables on SDRAM reads and writes even on 128-bit accesses,
- * but byte-enables don't exist on peripheral addresses, so align to 32-bit.
- */
-#define MAX_LITE_TRANSFER	(SZ_64K - 4)
-
 static inline struct bcm2835_dmadev *to_bcm2835_dma_dev(struct dma_device *d)
 {
 	return container_of(d, struct bcm2835_dmadev, ddev);
@@ -239,19 +226,13 @@ static irqreturn_t bcm2835_dma_callback(
 	d = c->desc;
 
 	if (d) {
-		if (c->cyclic) {
-			vchan_cyclic_callback(&d->vd);
-
-			/* Keep the DMA engine running */
-			writel(BCM2835_DMA_ACTIVE,
-			       c->chan_base + BCM2835_DMA_CS);
-
-		} else {
-			vchan_cookie_complete(&c->desc->vd);
-			bcm2835_dma_start_desc(c);
-		}
+		/* TODO Only works for cyclic DMA */
+		vchan_cyclic_callback(&d->vd);
 	}
 
+	/* Keep the DMA engine running */
+	writel(BCM2835_DMA_ACTIVE, c->chan_base + BCM2835_DMA_CS);
+
 	spin_unlock_irqrestore(&c->vc.lock, flags);
 
 	return IRQ_HANDLED;
@@ -358,6 +339,8 @@ static void bcm2835_dma_issue_pending(st
 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
 	unsigned long flags;
 
+	c->cyclic = true; /* Nothing else is implemented */
+
 	spin_lock_irqsave(&c->vc.lock, flags);
 	if (vchan_issue_pending(&c->vc) && !c->desc)
 		bcm2835_dma_start_desc(c);
@@ -375,7 +358,7 @@ static struct dma_async_tx_descriptor *b
 	struct bcm2835_desc *d;
 	dma_addr_t dev_addr;
 	unsigned int es, sync_type;
-	unsigned int frame, max_size;
+	unsigned int frame;
 	int i;
 
 	/* Grab configuration */
@@ -410,12 +393,7 @@ static struct dma_async_tx_descriptor *b
 
 	d->c = c;
 	d->dir = direction;
-	if (c->ch >= 8) /* LITE channel */
-		max_size = MAX_LITE_TRANSFER;
-	else
-		max_size = MAX_NORMAL_TRANSFER;
-	period_len = min(period_len, max_size);
-	d->frames = (buf_len - 1) / (period_len + 1);
+	d->frames = buf_len / period_len;
 
 	d->cb_list = kcalloc(d->frames, sizeof(*d->cb_list), GFP_KERNEL);
 	if (!d->cb_list) {
@@ -463,171 +441,17 @@ static struct dma_async_tx_descriptor *b
 				BCM2835_DMA_PER_MAP(c->dreq);
 
 		/* Length of a frame */
-		if (frame != d->frames - 1)
-			control_block->length = period_len;
-		else
-			control_block->length = buf_len - (d->frames - 1) *
-						period_len;
+		control_block->length = period_len;
 		d->size += control_block->length;
 
 		/*
 		 * Next block is the next frame.
-		 * This function is called on cyclic DMA transfers.
+		 * This DMA engine driver currently only supports cyclic DMA.
 		 * Therefore, wrap around at number of frames.
 		 */
 		control_block->next = d->cb_list[((frame + 1) % d->frames)].paddr;
 	}
 
-	c->cyclic = true;
-
-	return vchan_tx_prep(&c->vc, &d->vd, flags);
-}
-
-static struct dma_async_tx_descriptor *
-bcm2835_dma_prep_slave_sg(struct dma_chan *chan,
-			  struct scatterlist *sgl,
-			  unsigned int sg_len,
-			  enum dma_transfer_direction direction,
-			  unsigned long flags, void *context)
-{
-	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
-	enum dma_slave_buswidth dev_width;
-	struct bcm2835_desc *d;
-	dma_addr_t dev_addr;
-	struct scatterlist *sgent;
-	unsigned int i, sync_type, split_cnt, max_size;
-
-	if (!is_slave_direction(direction)) {
-		dev_err(chan->device->dev, "direction not supported\n");
-		return NULL;
-	}
-
-	if (direction == DMA_DEV_TO_MEM) {
-		dev_addr = c->cfg.src_addr;
-		dev_width = c->cfg.src_addr_width;
-		sync_type = BCM2835_DMA_S_DREQ;
-	} else {
-		dev_addr = c->cfg.dst_addr;
-		dev_width = c->cfg.dst_addr_width;
-		sync_type = BCM2835_DMA_D_DREQ;
-	}
-
-	/* Bus width translates to the element size (ES) */
-	switch (dev_width) {
-	case DMA_SLAVE_BUSWIDTH_4_BYTES:
-		break;
-	default:
-		dev_err(chan->device->dev, "buswidth not supported: %i\n",
-			dev_width);
-		return NULL;
-	}
-
-	/* Allocate and setup the descriptor. */
-	d = kzalloc(sizeof(*d), GFP_NOWAIT);
-	if (!d)
-		return NULL;
-
-	d->dir = direction;
-
-	if (c->ch >= 8) /* LITE channel */
-		max_size = MAX_LITE_TRANSFER;
-	else
-		max_size = MAX_NORMAL_TRANSFER;
-
-	/*
-	 * Store the length of the SG list in d->frames
-	 * taking care to account for splitting up transfers
-	 * too large for a LITE channel
-	 */
-	d->frames = 0;
-	for_each_sg(sgl, sgent, sg_len, i) {
-		unsigned int len = sg_dma_len(sgent);
-
-		d->frames += len / max_size + 1;
-	}
-
-	/* Allocate memory for control blocks */
-	d->control_block_size = d->frames * sizeof(struct bcm2835_dma_cb);
-	d->control_block_base = dma_zalloc_coherent(chan->device->dev,
-			d->control_block_size, &d->control_block_base_phys,
-			GFP_NOWAIT);
-	if (!d->control_block_base) {
-		kfree(d);
-		return NULL;
-	}
-
-	/*
-	 * Iterate over all SG entries, create a control block
-	 * for each frame and link them together.
-	 * Count the number of times an SG entry had to be split
-	 * as a result of using a LITE channel
-	 */
-	split_cnt = 0;
-
-	for_each_sg(sgl, sgent, sg_len, i) {
-		unsigned int j;
-		dma_addr_t addr = sg_dma_address(sgent);
-		unsigned int len = sg_dma_len(sgent);
-
-		for (j = 0; j < len; j += max_size) {
-			struct bcm2835_dma_cb *control_block =
-				&d->control_block_base[i + split_cnt];
-
-			/* Setup addresses */
-			if (d->dir == DMA_DEV_TO_MEM) {
-				control_block->info = BCM2835_DMA_D_INC |
-						      BCM2835_DMA_D_WIDTH |
-						      BCM2835_DMA_S_DREQ;
-				control_block->src = dev_addr;
-				control_block->dst = addr + (dma_addr_t)j;
-			} else {
-				control_block->info = BCM2835_DMA_S_INC |
-						      BCM2835_DMA_S_WIDTH |
-						      BCM2835_DMA_D_DREQ;
-				control_block->src = addr + (dma_addr_t)j;
-				control_block->dst = dev_addr;
-			}
-
-			/* Common part */
-			control_block->info |=
-				BCM2835_DMA_WAITS(BCM2835_DMA_WAIT_CYCLES);
-			control_block->info |= BCM2835_DMA_WAIT_RESP;
-
-			/* Enable */
-			if (i == sg_len - 1 && len - j <= max_size)
-				control_block->info |= BCM2835_DMA_INT_EN;
-
-			/* Setup synchronization */
-			if (sync_type)
-				control_block->info |= sync_type;
-
-			/* Setup DREQ channel */
-			if (c->dreq)
-				control_block->info |=
-					BCM2835_DMA_PER_MAP(c->dreq);
-
-			/* Length of a frame */
-			control_block->length = min(len - j, max_size);
-			d->size += control_block->length;
-
-			if (i < sg_len - 1 || len - j > max_size) {
-				/* Next block is the next frame. */
-				control_block->next =
-					d->control_block_base_phys +
-					sizeof(struct bcm2835_dma_cb) *
-					(i + split_cnt + 1);
-			} else {
-				/* Next block is empty. */
-				control_block->next = 0;
-			}
-
-			if (len - j > max_size)
-				split_cnt++;
-		}
-	}
-
-	c->cyclic = false;
-
 	return vchan_tx_prep(&c->vc, &d->vd, flags);
 error_cb:
 	i--;
@@ -796,7 +620,6 @@ static int bcm2835_dma_probe(struct plat
 	od->ddev.device_tx_status = bcm2835_dma_tx_status;
 	od->ddev.device_issue_pending = bcm2835_dma_issue_pending;
 	od->ddev.device_prep_dma_cyclic = bcm2835_dma_prep_dma_cyclic;
-	od->ddev.device_prep_slave_sg = bcm2835_dma_prep_slave_sg;
 	od->ddev.device_config = bcm2835_dma_slave_config;
 	od->ddev.device_terminate_all = bcm2835_dma_terminate_all;
 	od->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
@@ -886,5 +709,4 @@ module_platform_driver(bcm2835_dma_drive
 MODULE_ALIAS("platform:bcm2835-dma");
 MODULE_DESCRIPTION("BCM2835 DMA engine driver");
 MODULE_AUTHOR("Florian Meier <florian.meier@koalo.de>");
-MODULE_AUTHOR("Gellert Weisz <gellert@raspberrypi.org>");
 MODULE_LICENSE("GPL v2");
